Conventionally, as a vibratory actuator including a piezoelectric element, an actuator disclosed in PATENT DOCUMENT 1 has been known.
The vibratory actuator according to PATENT DOCUMENT 1 includes an actuator body formed of a piezoelectric element, and a driver element attached to the actuator body.
The actuator body is formed of a flat plate-shaped piezoelectric element having a longitudinal direction. In the actuator body, longitudinal vibration (so-called expanding/contracting vibration) along the longitudinal direction of the piezoelectric element and bending vibration (so-called lateral vibration) along a lateral direction of the piezoelectric element are induced in a cooperated manner by respectively applying alternating currents having different phases to two electrode pairs each of which includes two electrodes diagonally arranged. As a result, the driver element makes an orbit motion, more specifically, an elliptical motion in a plane of the piezoelectric element including a longitudinal direction and a lateral direction.
The vibratory actuator configured in the above-described manner is placed between a fixed body and a movable body placed to be movable relatively to the fixed body. Specifically, the vibratory actuator is provided so that the driver elements abut on one (hereinafter referred to as an “abutment body”) of the fixed body and the movable body and are fixed to the other one of the fixed body and the movable body. In this state, when the vibratory actuator is operated to cause each of the driver elements to make an orbit motion in the above-described manner, each of the driving elements makes an orbit motion with increased friction force while pressing the abutment body in an area where the orbit motion takes place, and the driver element makes an orbit motion while being spaced apart from the abutment body or with reduced friction force in the other area where the orbit motion does not take place. When each of the driving elements makes an orbit motion while pressing the abutment body, driving force is transmitted to the movable body through friction force between the driver elements and the abutment body to drive the movable body along a predetermined direction.
Reduction in size of the vibratory actuator described in PATENT DOCUMENT 1 is achieved by integrally burning the driver elements with the piezoelectric element.